Direct conversion of alcohols to acids



June-30, 1942. D. c. HULL l DIRECT CONVERSION OF ALCOHOLS TO ACIDS Filed sept. 7, 1958 zQRQQ MEM w Nm.

Patented June 30,1942

DIRECT CONVERSION F ALCOHOLS TO ACIDS David C. Hull, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application september '1, 193s, ser

6 Claims. (Cl. 260-531) Y than 150200 C. and usually at. temperatures in excess of 300 C. It has also been proposed to oxidize alcohols in aqueous solutions of chromates and other such oxidizing salts which may be regenerated electrolytically. However, these methods involve various complications. At present one procedure for treating alcohols comprises converting the alcohol to aldehyde and thereafter oxidizing thealdehyde to acid. However, this process is not direct; hence, requires considerable equipment and otherwise is not as satisfactory as my novel procedure to be described herein.

`I have found a simple, economical and eflicient method adapted for 'either small ror large scale operation, whereby various alcohols (primary or secondary) may be directly oxidized at relatively low temperaturesA and with large yields. I have found that, for example,.the various aliphatic alcohols may be converted directly to acids or if desired, acids `in admixture with various 'organic esters. The secondary alcohols may be converted to other type oxidation products by similar procedure. l

This invention has for one object to provide a process for the conversion of alcohols to acids. Another object is to provide an oxidation process which may be applied to either monoor polyhydroxy alcohols. Still-another object is to provide an oxidation process for treating alcohols which may be operated at relatively low temperatures and under ordinary pressure condi` tions.v Still another object is to provide a process for oxidizing alcohols whichv can, if desired, be

operated at either superatinospheric or reducedpressures. A still further lobject'is to provide a process particularly adapted for the direct conversion of lower aliphatic alcohols to lower aliphatic acids.

A still further object is to provide a process for the manufacture of mixtures of acids from alcohols. A still further object is to provide a process wherein an aliphatic acid may be pro- 55. the like. The gas is fed through conduit 2 t duced together with a content of the ester of said acid. Still another object is to provide an oxidation process which may be applied to alcohols in the presence of aldehydes. A still further object is to provide an ,oxidation process which is simple and eiiective and may be applied to a variety of alcohols and aldehydes.

Still another object is to provide a process particularly adapted for the direct conversion of ethyl alcohol or ethyl alcohol and acetaldehyde to acetic acid alone or in the presence of an acetate. Another object is to provide an oxidationlprocedure which may be applied to the conversion of.acetaldehyde together with an alcohol containing morethan two vcarbon atoms or an alcohol containing more than two carbon atoms in the presence of the-same-or a diierent aldehyde. Still another object is to provide a simple and edective procedure for the oxidation of polyhydroxy alcohols. Another object is to provide a method for converting an alcohol in the presence of an aldehyde, to mixtures of acids with esters.

A still further object isV to provide a novel catalyst containing liquid particularly adapted for the conversion of alcohols in the Vpresence of aldehydes directly toacids and esters. Still another object is to provide a method for activating and utilizing said catalyst. i

Agstill further object is to provide an apparatus particularly suitable for the direct conversion of alcohols in the presence of aldehydes to aliphatic acids, and, if desired, esters. Other objects will appear hereinafter.

I have found that if an alcohol, preferably in the presence of a content of aldehyde, is fed into the proper type catalyst solution, the alcohol. and any aldehyde may be oxidized directly to acid even though the catalyst is in the liquid condition and at relatively low temperatures. The corresponding aldehyde may be fed in with an alcohol to give the same acid, or different aldehydes and alcohols may be used to obtain mixed acids. The acids may be removed from the catalyst solution continuously as by distillation, for

example. 'Y AFor a further understanding of my invention, reference is made to the attached drawing. The

drawing is in the nature of `a diagrammatic sidemeans, as for example, the perforated thimble 4,

may be positioned in the column for dispersing the constituent fed in through conduit 2.

T'he column is also provided with a plurality of inlets 6 and 1 for alcohol and aldehyde. These components are supplied through tanks, metering devices or other such equipment designated 8 and 9. 'I'he alcohol and aldehyde are supplied from conduits II and I2, connected with suitable sources thereof, as will be discussed hereinafter.

Column 3 is connected by means of conduit I0 with a plurality of dephlegmators and condensers designated I3, I4 and I6. These devices may be supplied with cooling water, brine or other cooling medium, depending on the acid or ester being produced, its boiling point, and other such factors. One or more of these cooling devices may be interconnected through weir boxes such as I1 and I8 and conduits I9, 2| and 22, with the column and with acid receiver 23.

Receiver 23 may be used to collect the acid produced, the ester or. certain other constituents obtained from the process. These constituents may be drawn oil' through valved conduit 24 to distillation, extraction, Dyrolysis, esteriilcation or other treatment which it may be desired to apply thereto.

Conduit 26 is provided for conducting the uncondensed constituents to scrubbers 21 and 28. These scrubbers may be of more or less conventional construction. A suitable scrubbing liquid, as water, alcohol or the like, would be introduced through conduits 29 and 3| and withdrawn through conduits 3B and31 o the receivers positioned therebelow. The waste gas, usually nitrogen, if air has been used, together with some carbon dioxide and methane, escapes through conduit 34. The materials collected in receivers 32 and 33 may be withdrawn to distillation or l other treatment.

It is, of course, to be understood that suitable ow meters, thermometers, valves and other such devices would be employed in the setup for aiding in the functioning of the apparatus or rendering it automatic or semi-automatic. The parts exposed to contact with corrosive constituents l an understanding of my novel process, will be more apparent from the following examples. It is to be understood that these examples are set forth primarily for the purpose of illustrating my' preferred embodiment and they are not to be considered as a limitation upon my invention.

Example I.-Referring to the drawing, a run for producing acetic acid from ethyl alcohol will be described. Oxidation unit 3 was charged with a solution of cobalt acetate (CO(C2HO:)2.4H2O) used. In general,however, the catalyst solution will be comprised at least 50% or 60% of acid and in'many instances '75% or more of acid. Air was blown in through conduit I and conducted through conduit 2 into the oxidation column 3, passing through the perforated thimble 4. At the same time acetaldehyde was fed through the measuring device 9 into column 3 through conduit 1. This was continued until the catalyst solution turned from a pinkish color to a more or less dark green and the temperature o'f the unit was regulated to about between 60'10 C. This temperature was maintained by circulation of cooling medium in a cooling jacket surrounding the oxidation chamber.

Thereafter the ethyl alcohol to be oxidized was supplied to the unit through measuring device 8 and conduit 6.. The'supply of aldehyde and air through conduits 2 and 1 were continued. Acetic acid was' formed from the ethyl alcohol and distilled off through reflux condenser I3, and coolers I4 and I6 to acid receiver 23. The excess oxygen and nitrogen together with some noncondensible gases and small quantities of aldehyde, alcohol and acid, were conducted through conduit 26 to the scrubbers 21 and 28, where substantially all useful products were recovered by scrubbing. The gases were then discharged through conduit 34 to the atmosphere.

In this example the usual water azeotrope of ethyl alcohol was employed, However, it is possible to employ a more dilute alcohol, or i1' desired, an anhydrous alcohol may be supplied. The reaction was conducted in the liquid phase and at normal atmospheric pressure. However, superatmospheric pressure may be used.

Example II.-In this example an apparatus arrangement similar-to that of Example I was also employed. Approximately a total oi' 252 grams of aldehyde was fed into the catalyst initially for inducing a color change and for producing acid. During this oxidation an addition of 85.4 grams of 100% ethyl alcohol was fed. The resultant product indicated that 2.3% of the alcohol fed'had been converted to ethyl acetate, 31/2% unchanged and 94.2% converted to acid. A very small amount of non-condensible product such as carbon dioxide and methane were formed.

Eample IIL-In accordance 'with this example, 470 grams ofacetaldehyde were fed and 413.7 grams of 100% normal butyl alcohol added. 76.4% of the butyl alcohol was converted to butyric acid, 2.4% to butyl acetate and 1.03% to butyl butyrate. Approximately .26% remained unchanged. In this example, apparatus', catalyst and procedure similar to that described in detail with respect to Example I was employed.

Example IV.-In this run approximately pure oxygen, rather than air, was used as the oxidizing medium. 'Ihe catalyst-was initially treated with acetaldehyde as already described. Then a mixture of 95% normal butyl alcohol and 5% acetaldehyde (weight, percentage) were fed in.

in glacial acetic acid. While in this example ap- I proximately an8% solution. was employed, other Likewise, in this example the alcohol was oxidized to butyric acid.

While in the preceding examples cobalt acetate was used as a catalyst, inasmuch as this catalyst was available and found to give particularly good results, other metal salts may be employed. For example, mixtures 'of nickel and cobalt acetate were satisfactory. Nickel acetatel alone, functioned as a catalyst. Cobalt and copper acetate in admixture or copper acetate alone, may be employed. In general, I have found for my novel oxidation procedure that the 'various heavy metals ltion would or 80 C. If acids or esters of the higher acids i such as propionic or butyric acid were being prooperating at 300-600 C.

to aldehyde. This aldehyde was supplied through numbered from L-29, periodicsystem,`function satisfactorily in aliphatic acid solution. Preferably, the .organic salt of thesemetals, the salt -I being soluble in aliphatic acids, such as propionic and butyricacids, would be employed.

As indicated, other oxidizing medium besides air, such as relativelypure oxygen, may be used,

When pure oxygen is used, the catalyst is quite active and the alcohol may be fed more or less independent of the aldehyde supply. That isa small amount of aldehyde may be approximately simultaneously introduced with the alcohol or the aldehyde may be introduced at intervals." However, in my preferred processes, I carry out the alcohol treatment in the presence of at least a few percent of aldehyde. l

I have also found that various aldehydes may be introduced. For example, acetaldehyde in combination with ethyl alcohol or butyl alcohol function satisfactorily. Or, if desired, butyraldehyde or some other aldehyde in conjunction with the same or a different alcohol could be employed. While for treating constituents such as ethyl alcohol, acetaldehyde, etc., temperatures between 50-60 to 80 C. are preferred, other tempera.

tures may be employed, depending on the particular acids or esters being produced exemplified by temperatures below -145 C. In general, however, I prefer to maintain the lyst solution below the boiling point of the acid being produced. That is, ifv acetic acid is being produced, the temperature of the catalyst solube maintained at, for example, '70

duced, higher temperatures may be employed. For example temperatures as-high as 145 C. may be used in many instances. However, in general a temperature would not be employed, `under normal pressure conditions, greaterv 'than the boiling point of the acid being produced. Also, higher or lower'temperatures may b e employed, depending on whether superatmospheric or reduced pressure were appliedl to the process. In most instances catalyst concentration of 3% or 4% to 1215% in an aliphatic acid such as acetic acid functionslrsatisfactorily. However, these limits maybevaried somewhat.

' I have found that my process may be varied somewhat to produce results different' from those described in the preceding examples.

Example V.In accordance'with the procedure of this example, the process was carried out similar to that set forth in detail with respect tol Examples I, II, vIII and IV. However, in all instances,` the quantities of alcohol fed were increased substantially `over those specified and over that which the oxidation column was capable of oxidizing. In other words, a substantial excess of alcohol was supplied in each instance.. By this procedure a mixture of aliphatic acid and ester was obtained, the quantity of ester being as high as one-fourth to one-half of the alcohol supplied. 4

Example VI.-In accordance with another embodiment of my invention, the ester produced in the process was separated and fed through a dehydrogenation system operating ,at between about` 3509*-500J C The ester yielded aldehyde and acid. The aldehyde was employed as the aldehyde fed in runs similar to those described in Examples I-IV, inclusive. In another instance a portion of the alcohol was supplied through this system containing a dehydrogenation catalyst (copper), to convert the alcohol temperature of my cata- .along with the feed. The ester alone or the ester together with a content of water may be so circulated. That is, the ethyl acetate formed by the process'of Example II was fed along with thev new alcohol and aldehyde going 'to the apparatus. If desired. a content of water may be supplied along with the ester. I have found that by this procedure further ester formation maybe minimized. I have found that by recycling the ester further ester formation may be deterred and the reaction caused to' go in the desired direction, namely, the oxidation of the alcohol to acid. I have also found that merely adding water depresses ester formation. v

As indicated,vin the previous description, l1r prefer to carry out my alcohol oxidation in the presence of some aldehyde. I have found that aldehyde appears to assist in keeping the catalyst in 4the highest state of efficiency. The quantity of tion of oxidation products of polyhydroxy alcohols such as theglycols and glycerine. The process also may be employed to oxidation of secondary' alcohols with the resultant production of ketones,'for example.

Fromv the preceding examples, it may be seen that I have provided a novel, simple and eicient method for the direct oxidation'of hydroxy compounds. My process is economical and satisfactoryV for industrial operation, inasmuch as it readily functions at low temperatures and normal atmospheric pressure, giving high yields substantially greater than in many instances.

The process is flexible of operation and may be employed not only for the production of acids alone, but may be utilized to produce mixtures of acids such as mixtures of acetic and butyric acids. Or, the acids may be produced in the Either concentrated or diluted alcohols and aldehydes may be employed in my process. For example, the ordinary commercial azeotrope comprising ethyl alcohol and 5% water, functions satisfactorily in my process.

It is therefore apparent from the preceding, that my invention is susceptible of some modification; hence, I do not wish to be restricted therein, excepting insofar as is necessitated by the prior art and the spirit of the appended claims.

Having now particularly described my inventhe catalyst solution of a cobalt salt in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form a catalyst solution, introducing material amounts of a lower aliphatic alcohol and additional aldehyde into' said catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase, and subsequently recovering the aliphatic acid produced.

2. A process for the direct oxidation of a lower aliphatic alcohol for producing the corresponding aliphatic acid, which comprises treating a solution of a metal ion of a metal numbered 25 to 29 inclusive of the periodic table in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form a catalyst solution, itr ducing material amounts of a lower aliphatic' alcohol and additional aldehyde into said lcatalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in theliquid phase below 145 C.

3. A process for the direct oxidation of butyl alcoholl for' producing butyric acid which comprises treating a solution of a metal-ion of a metal numbered 25 to 29 inclusive of the periodic table in an aliphatic acid with an aldehyde and a gaseousl oxidizing medium to form a catalyst solution, introducing material amounts of butyl alcohol and acetaldehyde into said catalyst solution, oxidizing the butyl alcohol of the resulting solution of catalyst. alcohol and aldehyde by ytreating said solution with a gaseous oxidizing medium, and maintainingthe temperature of the solutionI of catalyst, butyl alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase.

4. A process for the direct oxidation of lower aliphatic alcohols to obtain the corresponding acids, which comprises preparing a solution of a metal ion of a metal numbered 25 to' 29 inclusive of the periodic table in an aliphatic acid as a catalyst solution, introducing material amounts of a lower aliphatic alcohol and lower aliphatic' aldehyde into said catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde by treating said solution with a gaseous oxidizing medium, and maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase.

5. A process for the direct oxidation of lower polyhydroxy aliphatic alcohols to obtain the corresponding acids, which comprises preparing a solution of a metal ion of a metal numbered 25 to 29 inclusive of the periodic table in an aliphatic acid as a catalyst solution, introducing material amounts of said lower aliphatic alcohol and a lower aliphatic aldehyde into said catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde by treating said solution with a gaseous oxidizing medium, and maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase.

6. A process for the direct oxidation of a lower `aliphatic alcohol to obtain the corresponding acid which comprises preparing a solution of a metal ion of a metal numbered 25 to 29 inclusive of the periodic tablein an aliphatic acid as a catalyst solution, introducing material amounts of a lower aliphatic alcohol and lower aliphatic aldehyde into said catalyst solution said alcohol being in substantial excess, oxidizing the alcohol of the resulting -solution ot catalyst, alcohol and aldehyde by treatingsaid solution with a gaseous oxidizing medium, and maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase.

' DAVID C. HULL. 

